Sign board - OVAL- elliptical column

[boobathims]

Dear forum members
I am designing a Signboard structure of 150' supported by 4 -oval shaped large columns braced at 3 levels.
1) Is there any reference for oval columns
2) How to design longitudinal and horizontal stiffener (local buckling )
3) How to do fatigue analysis & There is a opening for human to enter and work also

Thanks in advance
M.S.Boobathi

 

[KootK]

Neat.

1) I'm not aware of one. References for built up columns may be as close as you get.

2) I've usually stiffened to get b/t ratios down to AISC limits.

3) See AASHTO's guide on signs an luminaries and Tubular Steel Structures by Troitsky.

I find that quite a bit of judgement is required for these kinds if designs. Not particularly helpful, I know.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[SAIL3]

This is a very large section of unsupported pl......I am not aware of any info on anything similar(not saying that it is not out there)....I assume the OP is concerned with local pl buckling and so would I....as a result, I would tend to go with a circular shape where I am more certain of it's behaviour...

 

[KootK]

Depending on the needs of the project, there may be some logic in going with a circular shape as the structural column, as SAIL3 suggests, and just constructing the oval as cladding.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[structSU10]

Yea, maybe it is possible to do a subframe made of angles or something, that is essentially clad to create the oval. It can be trussed between faces (if possible) to make a fairly robust structure.

 

[KootK]

If the oval is to be the true structure, I expect that it would need to be spliced twice along its length. That probably means expensive field welding, especially if it needs to look sexy. A CHS spine could just be bolted together with flanged connections.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[azcats]

As others have noted, it will likely be more economical to the owner to use large diameter steel pipes inside a decorative skin that makes the oval shape. This is common in the sign industry.

Pipe is fast and easy to fabricate. There are several places around the country that can roll custom, large diameter pipe. You can step it down with telescope splices to keep shipping lengths reasonable. Or use bolted flanges as KootK suggested.

The fabrication costs to make the 'oval' shape structural just seem like they'd be excessive.

 

[rb1957]

second, 3rd?, that ... structural circular columns with a façade, which you could make into a true (truer?) oval.

another day in paradise, or is paradise one day closer ?

 

[BUGGAR]

Check out the design of monopole utility structures. Valmont makes these in multi-faceted tapered poles up to any length. These probably aren't what you want but will get you started on details like manways, connections and references to the appropriate codes covering these things. The baseplate alone will give you many happy hours.

I remember I designed a similar pole using API formulas for line piping, but I think AISC now has better coverage for large diameter HSS. For elliptical sections, I figured local buckling based on the tight radius for strong axis bending and on the long radius for weak axis bending. Vibrations and fatigue are big deals. Don't forget bird screens, guano is corrosive.